but the retention of en ##ant ##iom ##eric excess suggests that the auxiliary directs the cy ##cl ##ization . ) ti ##us ' s allen ##yl substrates can exhibit axial to te ##tra ##hedral chi ##ral ##ity transfer if en ##ant ##io ##pur ##e allen ##es are used . the example below generates a chi ##ral di ##os ##ph ##en ##pol in 64 % yield and 95 % en ##ant ##iom ##eric excess . ti ##us has additionally developed a camp ##hor @ - @ based auxiliary for ac ##hir ##al allen ##es that was employed in the first as ##ym ##metric synthesis of rose ##op ##hil ##in . the key step employs an unusual mixture of he ##xa ##fl ##uo ##ro @ - @ 2 @ -
but the retention of enantiomeric excess suggests that the auxiliary directs the cyclization. ) tius's allenyl substrates can exhibit axial to tetrahedral chirality transfer if enantiopure allenes are used. the example below generates a chiral diosphenpol in 64 % yield and 95 % enantiomeric excess. tius has additionally developed a camphor @ - @ based auxiliary for achiral allenes that was employed in the first asymmetric synthesis of roseophilin. the key step employs an unusual mixture of hexafluoro @ - @ 2 @ -